1. Field of the Invention
This invention relates generally to a pressure modulator valve device and more specifically to a pressure modulator valve device for modulating a pressure to suitably different pressures each of which serve to operate different fluid pressure operated devices, for example, a servo, an actuator, a valve etc., which are disposed in an oil pressure circuit in an automatic transmission wherein the pressure modulator valve device includes a plurality of modulator valves each having a cam for changing a modulating characteristic thereof and each operated by the same input.
2. Description of the Prior Art
In general, a throttle responsive pressure corresponding to the degree of opening of a throttle valve in an internal combustion engine of motor vehicle is, for example, used for controlling a main pressure which acts on a fluid operated servo for a friction clutch or a friction brake disposed in an oil pressure circuit of an automatic transmission. The throttle responsive pressure controls a shift valve that receives a governor pressure corresponding to vehicle speed, said shift valve transmitting the main pressure to a selected fluid operated servo. In order to accomplish a smooth shift control in the automatic transmission, it is desirable that the throttle responsive pressure for controlling the main pressure and the throttle responsive pressure for controlling the shift valve are of a different value.
Therefore, in conventional pressure modulator valve devices, the valve comprises a plurality of modulator valves each having a cam for determining a modulating characteristic thereof wherein each cam is interlocked to a throttle valve. In this type of valve, however, each cam is independently mounted on the modulator valve. As a result, a member for supporting a cam must be provided for each modulator valve. This can create an intricate mechanism and an associated scaling-up of the modulator valve.